Pseudomonas aeruginosa is the major cause of chronic respiratory infections in cystic fibrosis (CF) leading to persistent inflammation, lung tissue damage and high morbidity and mortality in this most common inheritable disease in Caucasians. The initially invading strains of P. aeruginosa are nonmucoid, but concomitantly with the establishment of a chronic infection, mucoid mutants overproducing the exopolysaccharide alginate emerge. The chronic infection, and additional host and bacterial factors that are not fully understood, lead to increased inflammation and irreversible tissue damage. This laboratory has previously described the mechanism of conversion to mucoidy which occurs via muc mutations that lead to the activation of the alternative sigma factor AIgU, the P. aeruginosa ortholog of the bacterial extreme stress sigma factor sigma-E. While alginate overproduction plays a role in reducing pulmonary clearance, we hypothesize that additional factors, co-expressed with alginate upon activation of AlgU, may contribute to pathogenesis in CF, since sigma factors normally direct transcription of a large number of gene subsets. So far, we have identified 10 additional genes controlled by A1gU that are activated in muc mutants. Importantly, a significant portion of these genes encode lipoproteins. Since lipoproteins play a role in innate proinflammatory signaling, we additionally hypothesize that P. aeruginosa products co-expressed with mucoidy contribute to inflammation in CF via pattern recognition receptors. Here we propose to: 1.further identify P. aeruginosa genes whose expression is activated in mucoid cells using conventional methods and techniques of global expression profiling; 2.analyze P. aeruginosa proinflammatory products associated with conversion to mucoidy; 3. analyze the role of pattern recognition receptors and signaling pathways involved in innate host response to P. aeruginosa products; and 4. study proinflammatory signaling in CF in combination with altered responses in CF cells. The specific alms of this proposal are to: 1) Identify P. aeruginosa genes that are activated or otherwise affected during conversion to mucoidy. 2) Determine how products of mucoid P. aeruginosa contribute to inflammation in CF. 3) Examine how proinflammatory products of mucoid P. aeruginosa synergize with the basic defect in CF and its downstream physiological effects, leading to exacerbation of pulmonary disease. These studies are expected to improve our understanding of respiratory pathogenesis in CF, and lead to new treatments of presently incurable lung infections associated with this disease.